Monroe County Emergency Management Director David Chambers estimated Sunday that the crash in the Cherokee National Forest left a debris field at least a half mile (.8 kilometer) long. Rescuers were unable to reach the plane’s cockpit before suspending operations Sunday, Chambers told WATE-TV.

The plane was based at Naval Air Station Meridian in Mississippi, part of one of five naval air training wings. Student pilots typically begin flying the T-45C after earlier training on a propeller aircraft.

In April, the Navy grounded its fleet of T-45C Goshawks amid reports of problems with the cockpit oxygen systems, later limiting them to low-altitude flights. Pilots said they were experiencing oxygen deprivation, prompting concerns from elected officials including U.S. Sen. Roger Wicker, a Mississippi Republican. The T-45 returned to regular use in July, after Navy officials said they had fixed the problem.

At least three other T-45Cs assigned to NAS Meridian have had mishaps in the last three years. A Goshawk assigned to Meridian skidded off the end of a runway in California on May 22, 2015, while the pilot was training to land on an aircraft carrier. The lone pilot was rescued from San Diego Bay by boaters. On Sept. 7, 2016, a jet crashed near the airfield at Meridian, with the student and instructor ejecting safely. Another Goshawk crashed Jan. 17 on the runway at NAS Meridian, with the pilots again ejecting safely.